It is known that various polymerization techniques may be used commercially in the production of selected polymeric materials. In many instances it is desirable to avoid the use of organic solvents in these production methods. Polymers prepared in aqueous mediums are favored in many industries because of their relatively low cost, ease of handling, and reduced low environmental problems. There are many instances however where it is required to attain a high solubility of the polymetric material in the reaction medium; however, since the solubility of polymers in aqueous solutions is generally low, aqueous mediums are not acceptable in these instances.
To fill the requirements of high polymer solubility together with relatively low cost, ease of handling and reduced environmental problems, emulsion polymerization has been used. In emulsion polymerization, the polymeric particles are generally homogeneously distributed in the water phase and therefore permit a higher concentration to be attained during the reaction. It is desirable in several industries to attain very high polymeric concentrations because of final product yield requirements. Such industries include toner preparation for office copiers, paint compositions, printing inks, photographic emulsions, adhesive products and cosmetic products. The commercially available emulsion polymerization methods used today generally yield weight percentage of solid contents in the 10% to 65% range. While the high end of this range could be marginally acceptable for some of the above rated industries, generally the emulsion polymerization procedures used are not adequate when a high solid content is needed. One of the reasons for this lack of high solid content, is because of the instability of the oil-in-water micelles and the difficulty of the heat transfer during the exothermic polymerization.
As noted above the presently available aqueous and emulsion polymerization methods have serious drawbacks in industries where high concentration of polymer is required.
This invention relates to an emulsion polymerization process for the preparation of high concentrations of polymers, homopolymers, copolymers, terpolymers and tetrapolymers. To solve the above noted problems of prior art emulsion polymerization methods, the present invention utilizes very small drop size of monomers during the monomeric addition steps.
The amount of emulsifier should be added in an amount of about 6%-10% of the total monomer to be added in the process. Thus, if 100 grams of monomer is to be ultimately added, from 6 to 10 grams of emulsifier should be added and slow heat dissipation should be maintained. Thus, the present invention, provides a novel method for attaining solid content concentrations of emulsion polymers ranging from about 65% to about 80% by weight of the emulsion.